This invention relates to the field of medical devices, and more particularly to a balloon catheter having a reinforcing mandrel.
Catheters designed for intravascular procedures such as angioplasty have a number of desirable characteristics. Such catheters must be able to transmit force along the length of the catheter shaft to allow it to be pushed through the vasculature. However, the catheter shaft must also retain sufficient flexibility to allow it to track over a guidewire through the often tortuous vasculature. Additionally, the catheter also must be able to cross stenosed portions of the vascular anatomy.
To help meet the desire for a catheter having sufficient pushability and crossability, while maintaining trackability, prior art designs have supplemented polymer catheter shafts with a stiffening wire or mandrel. Other prior art designs have addressed these handling and performance issues by using materials of different stiffness for the proximal and distal portions of the catheter, and employing a high strength metallic proximal shaft section, commonly called a hypotube. To prevent kinking at the junction of these two materials, while maintaining trackability and pushability, some conventional designs have employed a stiffening wire to bridge the transition in catheter shaft material. Despite these attempts, prior art designs have suffered from various drawbacks. For example, support mandrels do not always transmit axial force effectively.
Accordingly, it would be a significant advance to provide a catheter having improved pushability and crossability while maintaining good trackability. This invention satisfies these and other needs.
The invention is directed to catheters having supporting mandrels to improve pushability and trackability. The mandrel is constrained within the catheter shaft by being located within a dedicated mandrel lumen or secured at least in part directly to the catheter shaft. The length and position of the mandrel Within the catheter shaft may vary, so that the mandrel extends distally from the proximal end of the catheter shaft, or alternatively, from a location distal to the proximal end of the catheter shaft. The term mandrel should be understood to include a variety of different supporting members such as solid or hollow rods, wires, and the like.
One embodiment of the catheter of the invention comprises an inner tubular member defining a guidewire lumen and an outer tubular member coaxially or eccentrically disposed about the inner tubular member to form an annular inflation lumen, with a side wall which extends longitudinally within the annular inflation lumen and which defines a mandrel lumen configured to receive a mandrel therein. In a presently preferred embodiment, the sidewall extends along at least a portion of an inner surface of the outer tubular member. However, the sidewall may alternatively extend along at least a portion of an outer surface of the inner tubular member. The reinforcement provided by the mandrel improves pushability and columnar strength of the catheter shaft formed from relatively soft materials, while inhibiting or preventing shaft kinking. This aids manufacturing by offering better bonding to balloon materials and allows greater flexibility in catheter design. These designs also permit a reduction in wall thickness to maximize the inflation lumen. The mandrel lumen may be configured to allow the mandrel to be exchanged to adjust the handling characteristics of the catheter. Thus, in one embodiment, the mandrel lumen extends to the proximal end of the shaft to facilitate mandrel exchange. Alternatively, the mandrel may be secured within the lumen, at one or more points on the mandrel.
Another embodiment comprises a mandrel having a proximal end distal to the proximal end of the catheter shaft. In a presently preferred embodiment, the mandrel is in an intermediate portion of the shaft between proximal and distal shaft portions. The intermediate portion typically has a length less than the length of the proximal or the distal shaft sections. The mandrel may be within a sidewall portion defining a mandrel lumen or alternatively, may be secured to the catheter shaft at the proximal and distal ends of the mandrel, or along the length thereof from the proximal to the distal end of the mandrel. In a presently preferred embodiment, the mandrel is within the lumen of a side wall which extends longitudinally along at least a portion of an inner surface of the outer tubular member. The proximal and distal portions of the outer tubular member have conventional profiles, and form the inflation lumen in conjunction with the coaxial inner tubular member. The intermediate portion has a sidewall portion configured to define a mandrel lumen along its inner surface. The mandrel is typically secured within the lumen, preferably by heat deformation. In coronary artery applications, the mandrel is configured to support the catheter as it bends through the aortic arch and enters the coronary artery. Preferably, the portion of the catheter carrying the mandrel does not enter the coronary artery.
In other embodiments, the mandrel is secured along the length of the mandrel from the proximal to the distal end thereof directly to the inner tubular member or to the outer tubular member, without a sidewall mandrel lumen. In another embodiment, the catheter has rapid exchange capabilities and generally comprises an elongated proximal tubular member having a sidewall configured to define a mandrel lumen extending longitudinally along an inner surface of the proximal tubular member. An inner tubular member overlaps the distal portion of the proximal tubular member and provides a guidewire lumen with guidewire entry and exit ports. A distal tubular member secures the adjacent portions of the proximal tubular member and the inner tubular member and carries a balloon, such as a dilatation balloon, on the distal end. The support mandrel is disposed within the mandrel lumen. Restraining the support mandrel within the lumen provides superior transmission of axial forces to improve pushability. Moreover, the dedicated lumen addresses failure concerns by allowing the catheter to be withdrawn intact in case of a mandrel fracture. When the mandrel is not confined to a dedicated lumen, a fractured end could penetrate the catheter shaft or otherwise prevent its easy removal through the tortuous vasculature.
The catheter of the invention having a mandrel has excellent crossability and trackability. The mandrel connected to the catheter shaft directly or within the dedicated mandrel lumen provides effective transmission of axial force and avoids the entanglement of the mandrel around the inner tubular member by preventing movement of the mandrel within the annular lumen. The catheter of the invention also has a low profile shaft design, and provides suitable stiffness transitions between proximal and distal portions of the catheter to improve handling and performance and minimize kinking. These and other advantages of the invention will become more apparent from the following detailed description and exemplary drawings.